Using Grove NFC with Photon in I2C

Firmware
1

Hi, I want to use a Grove NFC board with my Photon with I2C (All the hardware modifications on the board is done) and all the libraries and threads I find are hard to follow and every one I flashed on my board couldn’t find the chip. I just want to read a tag and send it’s information to the cloud.

2

The first step when experiencing I2C issues would be running an I2C scanner app to see whether the communication is working at all.

Here is one such scanner app.

3

I ran the scanner and it found the device at 0x24 I2C Scan and when I try a firware that tries to read a tag from the board it detects the chip but not the tag.

#define SYSTEM_THREAD(ENABLED)
#include <Adafruit_PN532.h>
#define PN532_I2C_MODE
// #include <Wire.h>
// #define PN532_MODE (PN532_I2C_MODE)
// #define PN532_READY                         (0x01)
// #define IRQ_PIN  (D0) // This is how the PN532 Shield gets ready status in I2C mode
// #define RST_PIN  (D1) // Necessary for I2C mode

Adafruit_PN532 nfc(D0,D1);


void setup(void) {
  Serial.begin(115200); // Make sure your serial terminal is closed before power the Core.
  
   
  Serial.println("Hello!");

  nfc.begin();

  uint32_t versiondata;
  
  do {
    versiondata = nfc.getFirmwareVersion();
    if (!versiondata) {
      Serial.print("Didn't find PN53x board\n");
      delay(1000);
      Particle.process();
    }
    Particle.process();
    
    
  }while(!versiondata);
  
  

  // Got ok data, print it out!
  Serial.print("Found chip PN5\n"); Serial.println((versiondata>>24) & 0xFF, HEX); 
  Serial.print("Firmware ver. \n"); Serial.print((versiondata>>16) & 0xFF, DEC); 
  Serial.print('.'); Serial.println((versiondata>>8) & 0xFF, DEC);
  
  // configure board to read RFID tags
  nfc.SAMConfig();

}


void loop(void) {

  Particle.process();
  Serial.println("Waiting for an ISO14443A Card ...\n");
  delay(1000);
  
  
  uint8_t success;
  uint8_t uid[] = { 0, 0, 0, 0, 0, 0, 0 };  // Buffer to store the returned UID
  uint8_t uidLength;                        // Length of the UID (4 or 7 bytes depending on ISO14443A card type)
    
  // Wait for an ISO14443A type cards (Mifare, etc.).  When one is found
  // 'uid' will be populated with the UID, and uidLength will indicate
  // if the uid is 4 bytes (Mifare Classic) or 7 bytes (Mifare Ultralight)
  success = nfc.readPassiveTargetID(PN532_MIFARE_ISO14443A, uid, &uidLength);
  
  if (success) {
    // Display some basic information about the card
    Serial.println("Found an ISO14443A card");
    Serial.print("  UID Length: ");Serial.print(uidLength, DEC);Serial.println(" bytes");
    Serial.print("  UID Value: ");
    nfc.PrintHex(uid, uidLength);
    
    if (uidLength == 4)
    {
      // We probably have a Mifare Classic card ... 
      uint32_t cardid = uid[0];
      cardid <<= 8;
      cardid |= uid[1];
      cardid <<= 8;
      cardid |= uid[2];  
      cardid <<= 8;
      cardid |= uid[3]; 
      Serial.print("Seems to be a Mifare Classic card #");
      Serial.println(cardid);
    }
    Serial.println("");
 
  }  else {
    Serial.println("nfc.readPassiveTarget Failed\n");
    
    }
}
4

D0 is the I2C data pin and D1 is the I2C clock pin, so you cannot use them as IRQ and RST pin too.
You need other pins for IRQ and RST

5

Alright that makes sense, but I don’t know what those pins are. The board has only power and SCL,SDA (That code is probably for another board Il’l admit it) And what I have found for the Grove board is just people saying they adapted the original arduino library but that thing has like 10 interdependent files.

6

I found a way to read it, I just need to find a way to interpret that data.

7

I found a way to read it, I just need to find a way to interpret that data.

The example code above you are using tells you that the UID (card/tag ID) is either 4 bytes or 7 bytes. the 4 bytes (32 bit) can be converted into an unsigned long number and the 7 bytes into an 8 byte (64 bit) number. Alternatively, they can be kept as byte arrays and compared byte to byte.
How else did you want to interpret the data?

9

Yeah so I used another code (a modified library of the board’s maker) and now I can red the payload on my tags.

10

Can you share the code you’re using?

11

That’s the library I used with the ReadTagExtended example. I had a couple of problems in the workbench with my includes but if you use this kind of synthax it should work fine

#include "../lib/Seeed_Arduino_NFC-master/src/NfcAdapter.h"
#include "../lib/Seeed_Arduino_NFC-master/src/PN532/PN532/PN532.h"
#include <Wire.h>
#include "../lib/Seeed_Arduino_NFC-master/src/PN532/PN532_I2C/PN532_I2C.h"
12

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